DENVER (AP) — A late-night effort to repeal marijuana legalization in Colorado fell short Monday, when senators backed off a plan to pass a measure that would have opened the door to undoing last year’s vote to legalize pot.

The Senate faced a midnight deadline to pass the repeal measure in order to meet a legislative deadline. Facing a filibuster threat and defeat in the House, senators backed off the plans and adjourned Monday just before 10 p.m. without advancing the repeal.

Senate President John Morse, who sponsored the repeal measure along with most other senators, described the repeal bill as an attempt to get the marijuana industry’s attention and urge their support for pot taxes, which require another vote this fall because of Colorado tax law.

“Here is the inherent problem: The marijuana industry has no incentive to support a tax increase it promised voters,” Morse said. The measure died just a few hours after it was introduced.

The last-minute maneuver infuriated marijuana legalization supporters, some of whom ran up several flights of stairs to testify against the measure when they got word it would be heard.

“You’re subverting the will of the voters,” argued Joe Megysy, spokesman for the Marijuana Policy Project, a major backer of last year’s pot measure.

Even House colleagues seemed taken aback by the late-night maneuver to ask voters again whether retail pot sales should be allowed.

“This has caught all of us a bit off guard,” said Rep. Dan Pabon, sponsor of a marijuana regulation measure in the House. He said the chances of the repeal measure getting the necessary two-thirds margin in House were “.001.”

A parents’ group that criticized the marijuana industry applauded the last-minute bill. They said voters didn’t understand last year that their pot vote didn’t automatically trigger tax implementation.

“We were promised revenues for our state and our schools,” Diane Carlson argued.

Senators did approve a measure to set a marijuana blood-level limit for drivers Monday. The Senate had earlier rejected several similar proposals.

After a tumultuous day debating marijuana, the Senate left without voting on a regulation measure and a measure to tax recreation pot when sales begin in January.

On Tuesday, the Senate planned to consider a regulatory bill setting labeling requirements and advertising limits on retail pot. That bill included a first-in-the-nation attempt to treat marijuana magazines like pornography, forcing them behind the counter in stores that allow shoppers under 21. That provision, a last-minute amendment in the House, had High Times magazine contemplating a lawsuit if the requirement becomes law.

Taxing the newly legal drug was another question to be worked out. Senators were mulling a pot tax rate greater than 25 percent, a 15 percent excise tax for school construction and a special 10 percent cannabis sales tax. Those would be in addition to local and statewide sales taxes. The 25 percent tax rate has already cleared the House and was headed to the Senate floor Monday afternoon in largely the same form.